While most bacteria do have a cell wall, there are exceptions.

Mycoplasma is a genus of bacteria that lack a cell wall. They are known for being very small and are often referred to as "walking pneumonia" because they can cause respiratory infections.

The absence of a cell wall makes mycoplasma more flexible and resistant to certain antibiotics that target cell wall synthesis. However, it also makes them more susceptible to osmotic pressure changes.

It's important to remember that the vast majority of bacteria do have cell walls, and they play a critical role in the bacteria's survival and function.